The present invention relates to a method of reading data in a non-volatile memory device.
Recently, the demand has increased for a non-volatile memory device which electrically programs and erases data, and does not require a refresh function of periodically rewriting data.
The non-volatile memory device performs a program operation and an erase operation by changing a threshold voltage of a memory cell through movement of electrons by a high electric field applied to a thin oxide film.
The non-volatile memory device generally includes a memory cell array in which memory cells for storing data are disposed with a matrix shape, and a page buffer for programming data in a specific memory cell in the memory cell array or reading data from a given memory cell.
The page buffer has a pair of bit lines coupled to memory cells, a register for temporarily storing data to be programmed to the memory cell array or data read from a given memory cell of the memory cell array, a sensing node for sensing a voltage level of a specific bit line or the register, and a bit line select circuit for controlling connection of the bit line and the sensing node.
A read operation and a verifying operation in the non-volatile memory device determine whether or not a threshold voltage of a memory cell to be read is more than a read voltage or a verifying voltage.
However, the memory cell may be read with a threshold voltage different from a desired threshold voltage due to a change of temperature. As a result, a read margin is reduced or a state of a memory cell in accordance with the read operation and the verifying operation is different from a desired state.